looking to tune my car (clueless on this computer stuff)

ok my 91 mustang has its fair share of mods i'll list them

B-cam advanced 4 degress
thumper ported e7 heads
tmoss ported stock lower intake
gasket matched upper
73 mm vortech MAF
CAI
UD Pullies.
headers and Hpipe and bullet mufflers
190lph fuel pump
adj FPR

i am soon to be getting a 65 or 70 mm TB

i have played with timin and i have a FP guage on the rail with adj regulator so i can play with it some. but i feel there is some hidden power to be unleashed with some fine tuning.

i have had people mention tuning the computer. like they said about a programmer that you plug into the computer or something and you can mess with timing, A/F and the like. is this how they work?

i look around on the net and get super confused.

i would like my own programmer deal and not have to get a chip and be limited to my current combo, i would like to try diff things and tinker around.

can somone head me into the right direction?

i was reading about the tweecer.

leme see if i right.

there is a plug in that plugs to the EEC and holds the tune.

if u want to change it, take it off and plug it to your pc using a USB cable, create a new tune and plug the tweecer back into the EEC?

At present I'm not sure whether spending 400 plus dollars for your current set up...the hidden power you refer to is most often 10HP or less...money better spent on upgrading worn components or suspension.

5.0's are best tuned manually, computer tuning is not usually necessary....the EEC-IV is pretty loose and imprecise, tuning is far more important on the EEC-V system that the newer cars came with.

Honestly Ive had good luck tuning with just tweaking on the fuel ratio, reading the plugs, tweaking plug gaps, changing timing, and TPS voltage. Those are your best weapons in tuning a 5.0, and I've tuned a few headed/cammed 5.0's this way and gotten them to drive very well. Hell I tuned mine, over the long term, using this method doing it completely by ear smell and intuition, and when I finally got it dyno-tuned for a chip, they threw it on the dyno, added 2 degrees of total advance, not base, and said "well other than that, there isnt anything we can do, you had it perfect as it is". So I blew $450 for 3 things: EGR disabled, rev limiter disabled, and 2 degrees total timing added. Thats it!

how can i tinker with A/F without a computer deal?

all i can mess with is timing and fuel pressure

Fuel pressure changes your A/F ratio! If you change the fuel pressure behind the injector, when it fires, it fires more fuel because its firing at a higher pressure at the same pulse-width,

So when is a tweecer needed? After a certain amout of HP or boost? I'm clueless too.

IMO, I consider chip tuning necessary on speed-density motors which cant compensate as well, or when you just cant get it running well enough by other means, but as I said before the stock eec-IV will put up with a lot.

Dude you are way off. The only true way you can adjust your a/f is through the computer!


Yeah you can jack up the fuel press but guess what, the computer will adjust the duty cycle on the injectors to compensate for the fuel you are trying to force through it by jacking up the pressure. No it will not be instant but your EEC will make the changes slowly over the next 100 miles or so based off what the 02's read vs what they are commanded to read

True at part throttle the ecu will compensate after some time, but at WOT that is not the case.

From what I have seen, this applies to WOT as well

Yep. IIRC, the ECU can adjust the trim tables +/-10% to compensate, past that it hits its limit and I *imagine* would trigger a CEL for O2 rich/lean.

I've found in most cases, an ECU reflash just isnt necessary or worth the money. I have aluminum heads, a rather large cam for a daily driver, upgraded injectors, the list goes on.....and having a custom chip burned, which cost me over $400 including dyno time, yielded me less than 5 horsepower, and driveability was *barely* altered. Not worth the cash for an EEC-IV, now V is a different story......and I hear the SN-95 IV systems are a PITA also.

I can see your reasoning as I experienced the same thing when I had Panhandle Performance tune my car while on vacation a few years ago (except mine cost me $600) Got the car back, it still drove like **** unless at WOT and would go dead everytime you cut the a/c on.

This is the sole reason I went with a device that would allow me to do my own tuning.

I think the main benefit of tuning on a car that is only slightly modded is driveability. It will also let you squeeze out that extra few horspower. Its the little things that make the difference in the end. Also if you plan on upgrading in the future you will learn the basics of tuning and be ready to handle the more complex problems. You can change injectors when needed with a tuning program, have more cheaper options for MAF like lightning ones. OrLackThereof i respect what you say but agree to strongly disagree. I have had my tweecer on my 95 and will soon be putting it on my 1990ls. I never got it working completely on my 1995 but the car had a lot of other problems at the time that the tune couldnt fix. I really feel like tuning helps you understand your car, you get it running at its optimum, and have all the driveability of a stock car.

I agree with that. My knowledge sky rocketed when I started tuning. The EEC is nothing to be scared to learn because it makes everything so much simpler and easier to troubleshoot when you are having problems

I'm just going by my own experience, but as I mentioned, aftermarket heads, a big cam, 75mm intake, injectors, pretty much every bolt on available, and a tune did very very little for me driveability wise, the stock computer handled it all just fine. Also just finished tweaking on another guy's car, also headed/cammed/etc, also running a stock chip and A9P, and he has no driveability issues either.

You mentioned you have a 95, that's probably got a lot to do with it....talking to the local tuners, they've all told me the 94-95's had "bastard-computers" that were tweaked around from a standard EEC-IV before they introduced V, which gave them a host of unique problems.

I do have more experience and knowledge of the 94-95 computers, and have not done tuning on my 1990lx yet with my tweecer. I also know that the fox computers are much more forgiving and will take mods better. I was just stating that by personally tuning you can solve pretty much any driveability issues, and you learn a lot of the way the car works. While doing that you should gain some horsepower at the same time.

Yeah I understand what you're saying and I'm sure the newer ones are much trickier....and yes a twEECer is a great tool...I'm just saying that IMO, your average fox-driver will be better off spending that money on something else. But you never know, depends on the car and combination.

Hey, my buddy has a 90 lx blown 306 stock ecm and it runs like a champ, i went with a blown 347 and couldn't get my car to come close to where my freinds was running so i had to get a chip. So if u play with the timing and fuel pressure also spark plug gap and heat range u can get the car to run pretty good, if u can't, get it to run right get something that will help u out with that. Had the car at the dyno, had a custom chip burnt for it, it ran ok, the check engine lite came on. Started to loose fuel volume(dirty fuel filter), the dyno guy wanted me to buy another fuel pump, IMO u should try it out yourself to see if u can get it right,your mass air meter sucks, had it, got rid of it, my freind had it and got rid of it, pro m is better, or the store that took it over. Both cars has better heads and cam and exhaust work

I've read through a few forums and I may be missing it, but it seems nobody has explored hte option of using megasquirt. If you dont know, MS is a fully tunable ECU that is extremely cheap. You can buy a completed board cusomized for your car, for around $400, or you can get the board in pieces and solder it together your self for only $200. I recently set one of these up for a CBR 600 engine that was on our schools formula SAE race car. It was my first endevor in this type of thing and it was a moderatly easy project, even for a beginer like myself. After you get the board, you just need a laptop and then install the free tuning software. Then start setting up maps. It may seem confusing at first but there are tons of help forums for MS. Anyway, just a thought.